Semiconductor memory devices are used in integrated circuits for electronic applications, including cell phones, personal computer device, and televisions, as exampled. Commonly known memory devices include charge-storing devices, such as dynamic random access memory (DRAM) devices or flash memory devices.
A more recent development in memory devices involves magnetoresistive random access memory (MRAM) devices, in which data is stored by magnetic storage elements. The magnetic storage elements typically include two ferromagnetic layers that are separated by a thin tunnel barrier layer. For example, a magnetic tunnel junction (MTJ) is a component in the MRAM device and includes two magnetic layers separated by a thin tunnel barrier layer as mentioned above. In such an MTJ, a first magnetic layer is referred to as a fixed/pinned layer, while a second magnet layer is referred to as a free layer. On top of the MTJ, a conductive electrode typically provides a contact for electrically connecting to an interconnect structure (e.g., a conductive line and/or a conductive plug) and is fabricated during the MRAM back-end of line (BEOL) process.
However, with the development of new MRAM devices and the continuous shrinking of MTJ sizes, fabrication processes continue to become more difficult to perform and new challenges are being discovered.